Berkeley Lab, is
stable in air. The mixture’s energy properties show promise for use
in hydrogen fuel
cells. (Eun Seon Cho/Berkeley Lab)
(March 12, 2016) Berkeley
Lab innovation could lead to faster fueling, improved performance for
hydrogen-powered vehicles
Hydrogen is the lightest and most plentiful element on Earth
and in our universe. So it shouldn’t be a big surprise that scientists are
pursuing hydrogen as a clean, carbon-free, virtually limitless energy source
for cars and for a range of other uses, from portable generators to
telecommunications towers—with water as the only byproduct of combustion.
While there remain scientific challenges to making
hydrogen-based energy sources more competitive with current automotive
propulsion systems and other energy technologies, researchers at the U.S.
Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab)
have developed a new materials recipe for a battery-like hydrogen fuel
cell—which surrounds hydrogen-absorbing magnesium nanocrystals with atomically
thin graphene sheets—to push its performance forward in key areas.
Thin sheets of
graphene oxide (red sheets) have natural, atomic-scale defects that
allow hydrogen gas
molecules to pass through while blocking larger molecules
such as oxygen (O2)
and water (H2O). Berkeley Lab researchers encapsulated
nanoscale
magnesium crystals (yellow) with graphene oxide sheets to produce
a new formula for
metal hydride fuel cells. (Jeong Yun Kim)
The graphene shields the nanocrystals from oxygen and
moisture and contaminants, while tiny, natural holes allow the smaller hydrogen
molecules to pass through. This filtering process overcomes common problems
degrading the performance of metal hydrides for hydrogen storage.
These graphene-encapsulated magnesium crystals act as
“sponges” for hydrogen, offering a very compact and safe way to take in and
store hydrogen. The nanocrystals also permit faster fueling, and reduce the
overall “tank” size.
“Among metal hydride-based materials for hydrogen storage
for fuel-cell vehicle applications, our materials have good performance in
terms of capacity, reversibility, kinetics and stability,” said Eun Seon Cho, a
postdoctoral researcher at Berkeley Lab and lead author of a study related to
the new fuel cell formula, published recently in Nature Communications.
In a hydrogen fuel cell-powered vehicle using these
materials, known as a “metal hydride” (hydrogen bound with a metal) fuel cell,
hydrogen gas pumped into a vehicle would be chemically absorbed by the
magnesium nanocrystaline powder and rendered safe at low pressures.